A biofilm is a conglomerate of microorganisms embedded in a highly hydrated matrix of exopolymers, typically polysaccharides, and other macromolecules. Biofilms may contain either single or multiple microbial species and readily adhere to such diverse substrates as medical appliances (including catheters), soil, pipelines, teeth, mucous membranes, and heat exchangers. In certain environments, the colonizing microorganism is capable of growing in both biofilm (sessile) and free-living (planktonic) form, and the biofilm-associated cells may outnumber planktonic cells of the same species by a ratio of 1000-10,000:1. Although growth of the planktonic cells can be controlled by antimicrobials or sterilization treatment, the biofilm itself may be refractory to treatment, providing, in effect, a reservoir of cells, which can lead to recurrence of colonization, infection, and/or biofilm growth after treatment.
Prevention of colonization by microorganisms and eradication of biofilm-associated microorganisms is an important, and often difficult to solve, problem in many diverse fields. Unlike planktonic organisms, which are relatively susceptible to biocides, e.g. antibiotics, biofilm-associated microorganisms are often highly resistant to many antimicrobials. In one study, biofilm-associated bacteria were able to survive a concentration of antibiotic 20 times the concentration effective to eliminate the same species of bacteria grown in planktonic culture (Nickel, 1985). It is known that when organisms are isolated from biofilms and then grown in planktonic culture, they lose many of the characteristics associated with the biofilm progenitors, in particular, their resistance to antimicrobial treatment. In the biofilm, the glycocalyx matrix is one protective mechanism that provides a barrier against host defense mechanisms, such as antibodies and phagocytes, as well as from certain antimicrobial agents. Other possible reasons for the antimicrobial resistance of biofilms include the quiescent growth state of many of the microorganisms, substantially altered gene and protein expression profiles (as compared to planktonic cells), and the presence of “persisters”; subpopulations of microorganisms conferred with antimicrobial resistance in a stochastic manner.
Although many compositions are known in the art for treating substrates to render them resistant to biofilm formation, there continues to be a desire to provide further improved compositions for the treatment of substrates, in particular polymer surfaces, ceramics, glass and stone, in order to render them further biofilm resistant, and easier to clean.